Electric motor with noise reduction, in particular for a rail vehicle

Abstract

The electric motor (10) comprises a stator (16) and a rotor (12), a fan (17) driven in rotation by the rotor (12), and a fixed flange (18) defining at least one air inlet opening (24). Closing means (28) are movable between a first open position for each opening (24) and a second closed position for each opening (24). Elastic return means (34) return the closing means (28) to the open position, the closing means (28) being driven to the closed position by a centrifugal force induced by the moving rotor (12).

Description

[0001] The present invention relates to an electric motor, in particular for a railway vehicle.

[0002] An electric motor comprising a rotor and a stator is already known in the state of the art. In particular, open motors are known, which, for reasons of cooling the electric motor, have a defined air passage between the rotor and the stator, and a fan carried by the rotor and driving the air circulating in the air passage. Closed motors are also known, which do not have such ventilation, the rotor being enclosed to prevent the entry of polluting elements into the motor. A closed motor is preferable for use in a polluted environment, but less thermally efficient.

[0003] The present invention aims in particular to improve such an electric motor, by proposing a motor having the advantages of an open motor and a closed motor, and also in particular by reducing the noise emitted by this electric motor at high speed.

[0004] To this end, the invention relates in particular to an electric motor, comprising a stator and a rotor movable in rotation about an axis of rotation, at least one air passage being defined between the rotor and the stator, and comprising a fan driven in rotation by the rotor, and a fixed flange defining at least one air passage opening communicating with the air passage, characterized in that the electric motor comprises means for closing each air passage opening, movable between a first position for releasing each opening and a second position for closing each opening, the closing means being configured to move into the closing position when the rotor has a rotation speed greater than a predefined threshold.

[0005] The inventors found that the noise level at high speed is mainly due to ventilation. The present invention therefore proposes to close the air passage opening to prevent the passage of air into the internal ventilation at high speed.

[0006] Due to the use of the traction motor, this reduction in airflow is not harmful at high rpm, because the torque density at this speed is low.

[0007] Note that closing the opening also allows the engine to be considered a closed engine at high speed. On the other hand, the engine is considered an open engine at low speed or when stopped.

[0008] An electric motor according to the invention may further comprise one or more of the following characteristics, taken alone or in any technically conceivable combination. The closing means comprise at least one flap sized to cover at least one of the openings in the closing position. Each flap has a shape extending in an arc of a circle defined around the axis of rotation. The electric motor comprises means for elastically returning the closing means to the release position, the closing means being driven to the closing position under the effect of a centrifugal force induced by the moving rotor. The elastic return means comprise, for each flap, at least one spring, extending radially between a hub connected to the rotor and the corresponding flap. The stiffness of each spring is chosen so that the corresponding flap covers the corresponding opening(s) when the rotational speed of the rotor exceeds the predefined threshold.The electric motor comprises end-of-travel stops limiting the movement of the flaps, each flap coming into contact with a corresponding one of the stops in the closed position. The closed position is defined by the maximum length of the elastic return means. The electric motor comprises an electric actuator provided with radial rods movable radially, each rod carrying a flap, the electric actuator being configured to move the flaps according to the rotational speed of the rotor. The predefined threshold is substantially equal to half the maximum speed of the rotor. The opening is an air inlet opening for supplying air to the rotor. The opening is an air outlet opening for discharging air from the rotor.

[0009] The invention also relates to a railway vehicle, characterized in that it comprises an electric motor as defined above.

[0010] Various aspects and advantages of the invention will be highlighted in the following description, given solely by way of example and with reference to the appended figures, among which: [ Fig 1 ] There figure 1 is a partial longitudinal sectional view of an electric motor according to an exemplary embodiment of the invention, in a first configuration; [ Fig 2 ] There figure 2 is a view, in a sectional plane of the figure 1 , from the electric motor of the figure 1 ; [ Fig 3 ] There figure 3 is a view similar to the figure 1 of the electric motor in a second configuration; [ Fig 4 ] There figure 4 is a view similar to the figure 2 of the engine of the figure 3 ; [ Fig 5 ] There figure 5 is a view similar to the figure 1 of the electric motor in a third configuration; [ Fig 6 ] There figure 6 is a view similar to the figure 2 of the engine of the figure 5 . [ Fig 7 ] There figure 7 is a partial perspective view of an electric motor according to a second embodiment of the invention.

[0011] The figures show an electric motor 10, for example intended to equip a railway vehicle.

[0012] The electric motor 10 comprises, in a conventional manner, a rotor 12 secured to a shaft 14 which can rotate around a longitudinal axis X. The electric motor 10 also comprises, in a conventional manner, a stator 16.

[0013] The electric motor 10 also comprises a fan 17, kinematically connected to the rotor 12 so as to be driven in rotation by the latter.

[0014] The fan 17 is intended to drive an air flow, in particular in a first circumferential air passage 20 defined between the stator 16 and the rotor 12. Optionally, the rotor 12 also comprises at least one second air passage 22.

[0015] The electric motor 10 comprises a fixed flange 18. The flange 18 defines at least one air passage opening 24 communicating with the first air passage 20 and each second air passage 22.

[0016] In the example described, the opening 24 is an air inlet opening, for supplying the rotor with air for cooling purposes.

[0017] In the example described, the flange 18 defines a plurality of openings 24 (in particular eight openings 24). Thus, in the remainder of the description, the at least one opening 24 will be designated by the terms “the openings 24”. However, the case where the flange 18 would only have a single opening 24 is not excluded.

[0018] It will be noted that the stator 16 also advantageously comprises at least one third air passage 26.

[0019] It appears that part of the noise generated by the electric motor 10 is due to the air entering through the air passage openings 24. This part of the noise is predominant at high engine speed.

[0020] We have represented, on the figures 1 And 2 , the electric motor 10 stopped, on the figures 3 And 4 , the medium-speed electric motor, and on the figures 5 And 6 , the high-speed electric motor.

[0021] In the present description, the electric motor is considered to be at high speed when the rotational speed of the rotor 12 is greater than half of its maximum speed. The motor is at low speed or medium speed when the rotational speed of the rotor 12 is less than half of its maximum rotational speed.

[0022] In order to reduce the noise caused by air entering the air passage openings 24, the electric motor 10 comprises means 28 for closing the air passage openings 24. The closing means 28 are shown in more detail in the figures 2 , 4 And 6 .

[0023] The closing means 28 comprise at least one flap 30, movable between a first position for clearing the openings 24, and a second position for closing at least one of the openings 24.

[0024] Each shutter 30 is sized to cover at least one of the openings 24 in the closed position.

[0025] In the example described, the closure means 28 comprise four flaps 30, each being sized to cover two openings 24 in the closure position. Thus, in the description which follows, corresponding to a particular embodiment, the flaps 30 will be designated in the plural, without this excluding embodiments with a single flap.

[0026] Each flap 30 has, for example, a shape in the form of an arc of a circle defined around the axis of rotation X. Each flap 30 has a dimension, in a radial direction perpendicular to the axis of rotation X, greater than or equal to the dimension, in the same direction, of each opening 24 that it is intended to cover.

[0027] Optionally, the fan 17 comprises rails 32 for guiding the flaps 30. These rails 32 ensure the correct alignment of the flaps 30 during their movements between the release and closure positions. The rails 32 preferably extend radially from the axis of rotation X.

[0028] Advantageously, the rails 32 are formed from materials with a low coefficient of friction, so as not to oppose significant resistance to the movement of the shutters 30.

[0029] The closure means 28 further comprise means 34 for elastically returning the flaps 30 to their disengaged position. The elastic return means 34 comprise, for example, a spring 36 for each flap 30. Each spring 36 thus extends radially from the axis of rotation X, between a hub 38 connected to the shaft 14 and the corresponding flap 30.

[0030] The closing means 28 are driven towards the closing position under the effect of the centrifugal force induced by the moving shaft 14.

[0031] The stiffness of the springs 36 is chosen so that the centrifugal force is sufficiently high compared to the restoring force of the springs so that the flaps 30 cover the corresponding openings 24 when the rotational speed of the shaft 14 is greater than a predetermined threshold. The predetermined threshold corresponds, for example, to half the maximum speed of the rotor 12. Those skilled in the art will easily be able to determine the desired spring stiffness using simple force calculations.

[0032] We have represented, on the figures 3 And 4, an intermediate position of the flaps 30, when the engine is operating at medium speed, with a rotor rotation speed lower than said threshold. It is thus noted that the openings 24 are progressively covered as a function of the centrifugal force, therefore of the rotation speed of the rotor 12.

[0033] When the rotation speed of the shaft 14 is greater than said predetermined threshold, the flaps 30, due to the centrifugal force, completely cover the openings 24 as shown in the figures 5 And 6 . More particularly, the shutters 30 being in rotation around the axis of rotation X, the shutters 30 are dimensioned so that the openings 24 are closed substantially at each instant by the shutters 30 which come to cover them one after the other.

[0034] Advantageously, the motor 10 comprises end-of-travel stops 40, against which the shutters 30 come into contact in the closed position, as shown in the figure 6 . Alternatively, the movement of the flaps 30 is limited by the maximum length of the springs 36.

[0035] In this case, the air no longer rushes into the openings 24, thus eliminating the noise linked to this rush of air. This allows, in the example shown, a noise reduction of approximately 5 dB.

[0036] Due to the use of the traction motor, this does not involve any problems with motor overheating. Indeed, the traction motor, at high speed, is not thermally stressed due to the low torque density required at this operating speed and the high level of ventilation.

[0037] Due to the elastic restoring force, when the rotational speed of the shaft 14 decreases, and therefore the centrifugal force decreases, the flaps 30 are returned to the release position, gradually uncovering the openings 24 as a function of the speed.

[0038] It thus appears that the openings 24 are cleared, partially closed or completely closed, automatically, depending on the speed of rotation of the shaft 14.

[0039] Thus, the electric motor 10 operates as an open motor at low or medium speed (from zero speed up to said predetermined threshold, in particular up to a speed substantially equal to half the maximum speed), and as a closed motor at high speed (for a speed greater than said predetermined threshold, for example a speed greater than half the maximum speed).

[0040] It should be noted that operation with the motor closed also reduces pollution on the rotor since the air, which carries pollution, no longer circulates around the rotor when the flaps 30 are in the closed position.

[0041] It should be noted that the invention is not limited to the embodiment previously described, but could have various variants without departing from the scope of the claims.

[0042] In particular, the preceding embodiment describes sealing means for air inlet openings, but alternatively, sealing means for air outlet openings could also be provided. The engine could then comprise sealing means for the air inlet openings, or for the air outlet openings, or for both the air inlet openings and the air outlet openings.

[0043] On the method of realization of the Figure 7 , the passage openings are outlet openings 42, arranged in a flange 44 closing the motor 10 on a downstream side opposite the air inlet side.

[0044] The outlet openings 42 are each associated with a flap 45 movable between a release position (not shown) and a closure position (shown in the Figure 7 ).

[0045] The motor 10 then comprises an electric actuator 46 intended to maneuver the shutters 45 between their release and closure positions.

[0046] The electric actuator 46 is provided with radial rods 48 which are radially movable, each rod 48 carrying a respective flap 45.

[0047] The electric actuator 46 preferably includes a cover 50 for each rod 48 (one of the covers is not shown solely to show the rod).

[0048] The electric actuator 46 is configured to move the flaps 45 as a function of the rotation speed of the rotor 12. Thus, the electric actuator 46 is for example controlled by an automation device deciding the position of the flaps 45 as a function of the speed of the rotor 12.

[0049] The electric actuator 46 is configured so that the flaps 45 are in the closed position when the rotor speed exceeds the predefined threshold.

Claims

1. Electric motor (10), comprising a stator (16) and a rotor (12) rotatable about an axis of rotation (X), at least one air passage (20) being defined between the rotor (12) and the stator (16), and comprising a fan (17) driven in rotation by the rotor (12), and a fixed flange (18; 44) defining at least one air passage opening (24; 42) communicating with the air passage (20), characterized in that the electric motor (10) comprises means (28) for closing each air passage opening (24; 42), movable between a first position for releasing each opening (24) and a second position for closing each opening (24), the closing means (28) being configured to move into the closing position when the rotor (12) has a rotation speed greater than a predefined threshold.

2. Electric motor (10) according to claim 1, wherein the closing means (28) comprise at least one flap (30; 45) sized to cover at least one of the openings (24; 42) in the closing position.

3. Electric motor (10) according to claim 2, in which each flap (30; 45) has a shape extending in an arc of a circle defined around the axis of rotation (X).

4. Electric motor (10), according to claim 1, comprising means (34) for elastically returning the closure means (28) towards the release position, the closure means (28) being driven towards the closure position under the effect of a centrifugal force induced by the rotor (12) in motion.

5. Electric motor (10) according to claim 4, in which the elastic return means (34) comprise, for each flap (30), at least one spring (36), extending radially between a hub (38) linked to the rotor (12) and the corresponding flap (30).

6. Electric motor (10) according to claim 5, wherein the stiffness of each spring (36) is chosen so that the corresponding flap (30) covers the corresponding opening(s) (24) when the rotational speed of the rotor (12) exceeds the predefined threshold.

7. Electric motor (10) according to any one of claims 4 to 6, comprising end-of-travel stops (40) limiting the movement of the flaps (30), each flap (30) coming into contact with a corresponding one of the stops (40) in the closed position.

8. Electric motor (10) according to any one of claims 4 to 6, in which the closure position is defined by the maximum length of the elastic return means.

9. Electric motor (10) according to any one of claims 2 to 3, comprising an electric actuator (46) provided with radial rods (48) movable radially, each rod (48) carrying a flap (45), the electric actuator (46) being configured to move the flaps (45) as a function of the rotational speed of the rotor (12).

10. Electric motor (10) according to any one of the preceding claims, wherein the predefined threshold is substantially equal to half the maximum speed of the rotor (12).

11. Electric motor (10) according to any one of claims 1 to 10, wherein the opening (24) is an air inlet opening for supplying air to the rotor (12).

12. An electric motor (10) according to any one of claims 1 to 10, wherein the opening (42) is an air outlet opening for exhausting air from the rotor (12).

13. Railway vehicle, characterized in thatit comprises an electric motor according to any one of the preceding claims.

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